This invention relates generally to label tape printers and more particularly to label tape cassettes and their drive mechanisms.
Label tape printers and associated print cassettes have recently become popular. These printers have an ancestor in the form of the DYMO.TM. plastic label maker that was popular in the United States in the 1960's and 1970's. The DYMO machine embosses characters into plastic tape. See, for example, U.S. Pat. No. 4,624,590; and tape and ribbon cartridges described in U.S. Pat. Nos. 4,226,547; 4,391,539; and 4,678,353. A more recent label printer is the KROY lettering machine (Kroy, Inc., Scottsdale, Aeiz.). See, for example, U.S. Pat. No. 4,832,514, issued May 23, 1989, to Basile; and U.S. Pat. No. 4,836,697, issued Jun. 6, 1989, to Plotnick, et al. as well as U.S. Pat. Nos. 3,834,507; 4,243,333; 4,402,619; and 4,462,708. Hirosaki, et al., describes in U.S. Pat. No. 4,666,319, issued May 19, 1987, a typical printer in which character images are formed into strips of tape by transferring ink or other color from color carrying ribbon to the tape by localized application of heat and pressure. The new label tape printers are able to print a line of characters on an adhesive tape strip that is cut off at the end of the print line and which can be adhered to surfaces, similar to SCOTCH brand tape. The label tape used in these printers is special, and comes ready-to-use in a tape cassette that includes an ink ribbon for the print head. The finished tape output from the printer consists of three parts, a transparent tape on which ink is printed, a double sided, adhesive tape, and a backing that is subsequently peeled-off to expose an adhesive surface for applying the label tape to a desired surface.
The backing and adhesive tape are positioned on a first reel inside an unused cassette, the transparent tape is on a second reel, and the ink ribbon, usually of a thermal ink type, is provided on a third reel. Used ink ribbon is taken up on a fourth reel. To print a label, the ink ribbon and print head are brought into contact with the transparent tape. A reverse image is printed by the head on the transparent tape so that the image will read correctly when view through the tape. The transparent tape is thereafter pressed together with one side of the adhesive tape such that the printed ink is sandwiched between the two tape layers. In this manner, the printed ink will not be exposed and rubbed off. On the other surface of the adhesive tape is a peel-off backing material. After the two tape layers have been pressed together, the composite tape exits one end of the tape cassette, and a cutting unit usually cuts the tape after the line of print has been completed. The user then pulls the printed piece of label tape from the printer for use.
These printers employ a complex series of interconnected gears, pulleys, and rollers to manage the operations of printing, feeding, and tape assembly during use of the printer. See for background, U.S. patent application of Hiroki Godo, et al., Ser. No. 07/609,501, filed Nov. 11, 1990, entitled "Tape Printer", now U.S. Pat. No. 5,193,919. During the printing operation, it is important that the ink ribbon and transparent label tape move together at the same rate. This prevents the possible rubbing of the two together causing smudging of the ink on the label tape. The least amount of tape will be wasted if the label tape and the adhesive tape are pressed together and cut near the point of printing in the printer. However, to assemble these tapes, the ink ribbon must be moved out of the way as quickly as possible after serving its purpose at the thermal print head. Since the ink is deposited on the inside of the two sandwiched tapes, and since the tapes must be sandwiched very close to the point of printing, the ink ribbon, by necessity, must be positioned very close to the tape pressure roller assembly employed for pressing the two tape layers together. An extremely important function, therefore, of the printer gearing mechanism is to maintain the ink ribbon taunt in its travel through the printer so as not to interfere with other operating parts of the printer.
Most of the time the label tape and ribbon transport mechanism functions as intended. But in conventional label tape drive mechanisms, if a user pulls on a tape prior to being cut, the gear mechanism for the tape rollers and reels will be moved against the resistance of the tape transport motor and its associated high reduction gears. The usual and catastrophic result is that the ink ribbon becomes entangled and caught in the tape pressure rollers utilized for pressing the transparent tape to the adhesive tape. Once the ink ribbon has been ensnared between these rollers and tape layers, the entire cassette is of no further utility, and the damage cannot readily be undone or the tapes cannot be untangled. Moreover, cutting the tape off with the cutter also cuts the entangled ink ribbon. The ink ribbon cannot then be effectively fed onto its take-up reel because it is effectively out of operation. Given human nature, and a typical user's impatience with tape feeding and cutting, the above scenario is all too common an occurrence.
The present invention solves the above problem by allowing the user to proceed with early removal of the label tape from the printer, by arranging the gear mechanisms so that the gears are freed from enagement with the printer drive motor. The various tape and ink ribbon reels, gear mechanisms, and rollers will maintain their proper respective functions with the ink ribbon kept taunt by continually taken up on its take-up reel because tape tension does not become loose and tape to become pulled into the final tape assembly.
A second, related problem is also solved by the present invention. The adhesive tape has an exposed adhesive surface during its travel between the adhesive tape supply reel and the pressure rollers that combine the adhesive tape with the transparent tape.A guide roller is needed between the adhesive tape supply reel and the pressure rollers to keep the adhesive tape from wandering from its proper path of travel of dislocating and adhering to the inside walls of the cassetts, or worse, to the ink ribbon. But ordinary cylindrical guide rollers provide the adhesive tape with too much surface for attachment and, as a result, become attached to the guide roller surface, especially after long idle periods of nonuse of the printer. A guide roller having deep grooves and ridges, much like the appearance of a machine screw threaded stock, is employed to solve this problem.